System for and method of analyzing surface condition of PCB using RGB colors

ABSTRACT

A system for and a method of analyzing the surface condition of a PCB using RGB colors are disclosed. The analyzing method includes the steps of feeding a target PCB, to be measured, to an image pick-up position where a pick-up unit is disposed, by a feeding unit, picking up an image of a metal surface of the fed target PCB, extracting pixel data from the picked-up image for the target PCB, performing a mapping operation for RGB signals of the extracted pixel data in accordance with a mapping program, thereby determining relative RGB values, producing cumulative distribution data of the relative RGB values for the target PCB in accordance with an RGB-mapping process, and quantitatively determining the oxidation degree of the target PCB metal surface exhibited with the lapse of time, based on the cumulative distribution data. Since relative values of RGB colors in an image picked up from the metal surface of a PCB can be analyzed, it is possible to rapidly and easily analyze the surface condition of the PCB such as oxidation, contamination, or structural defects of the PCB in a quantitative manner without using an expensive surface analyzer.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a system for and a method ofanalyzing the surface condition of a printed circuit board (PCB) usingRGB colors and more particularly, a system for and a method of analyzingthe surface condition of a PCB using RGB colors, in which the oxidationdegree of the PCB is quantitatively measured, based on relative valuesof RGB signals, in unit pixels of an image obtained by picking up animage of the PCB.

[0003] 2. Description of the Related Art

[0004] PCBs, which are mounted thereon with electronic elements such assemiconductor chips, resistors, and capacitors, serve to electricallyconnect the mounted electronic elements via conductive wiring patternsof desired shapes or to supply a drive voltage to the electronicelements. Such a PCB includes a board for mounting electronic elementsthereon, and wirings of desired patterns for electrically connecting themounted electronic elements.

[0005] The configuration of such a PCB and the procedure formanufacturing the PCB will now be described in detail. A copper cladlaminate (CCL) is first prepared by forming a copper film on one surfaceor both surfaces of a thin substrate made of an insulating material suchas epoxy or bakelite resin. In order to increase the bonding force ofthe copper film to the resin of the substrate, the formation of thecopper film is carried out in such a manner that the copper film reactswith the resin of the substrate, thereby penetrating into the resin by acertain depth, for example, about 5 μm.

[0006] Thereafter, a shearing process is carried out so as to shear theCCL to have a desired panel size suitable for subsequent processes. Thesheared CCL is then subjected to a beveling process, so that it hasround corners. Subsequently, the CCL is subjected to a scrubbing processfor removing fingerprints or dust on the copper film surface of the CCLor providing roughness to the copper film surface in order to increasethe bonding force of a dry film to be laminated on the copper filmsurface in a subsequent lamination process.

[0007] After completion of the scrubbing process, the dry film is formedon the copper film surface. The dry film consists of a film-shapedphotoresist adapted to form a desired wiring pattern on a PCB, a Mylarfilm for providing a certain degree of flexibility, and a cover film.

[0008] An artwork film formed with a wiring pattern is then attached tothe dry film. Thereafter, the resulting structure is subjected to anexposure process in which ultraviolet rays are irradiated onto thestructure so as to cure portions of the photoresist reacting with theultraviolet rays. At this time, the other portions of the photoresist donot vary. A development process is then carried out using a certaindeveloper, thereby dissolving and, thus, removing uncured portions ofthe photoresist while leaving the cured photoresist portion to besubsequently used as an etch resist. Thus, an etch mask made of the etchresist is formed on the copper film of the CCL for formation of adesired wiring pattern.

[0009] After formation of the etch mask, an etchant is sprayed onto theresulting structure, thereby removing an exposed portion of the copperfilm corresponding to a region other than a wiring pattern region wherethe copper film is protected by the etch resist. Accordingly, a desiredwiring pattern is formed. After formation of the wiring pattern, theetch resist is completely stripped. Thus, the PCB is completed.

[0010] Such a PCB manufacturing method involves repeated processes oflamination, etching and cleaning of copper films, as described above.However, the final product, that is, the PCB, may have a poor surfacecondition due to contamination sources such as dust or fingerprints lefton the copper films, and oxidation or discoloration of the wiringpatterns.

[0011] In particular, where oxidation occurs at bonding pads of the PCB,made of a metal such as Cu, to be connected to corresponding portions ofa semiconductor chip, attachment of balls or wires may not be achieveddue to oxides present on the bonding pad surfaces. Although theattachment may be achieved, its bonding strength is considerably low.

[0012] Accordingly, it is necessary to measure the degree of anoxidation at the metal surface of a PCB enabling identification of theabove mentioned problem. Conventionally, this measurement is achievedwith the operator's naked eye or expensive equipment such as a surfaceanalyzer.

[0013] However, the method of visually inspecting the surface conditionof a PCB by the operator makes it difficult to obtain accurateinspection results because it is greatly influenced by variousparameters of the surroundings such as the ability of the operator,surrounding brightness, and time. Furthermore, this method has limitedrepeatability and reproducibility for the inspection results. For thisreason, there is a problem in that it is impossible to obtainquantitative data capable of determining respective qualities ofoptional PCBs.

[0014] On the other hand, where an expensive surface analyzer such asESCA or Auger is used, it can accurately measure the condition of themetal surface of an optional PCB. However, there are problems in thatthe surface analyzer increases the manufacturing costs of PCBs due tohigh installation costs thereof, and cannot be easily applied toproducts newly developed.

SUMMARY OF THE INVENTION

[0015] The present invention has been made in view of the abovementioned problems, and an object of the invention is to provide asystem for and a method of analyzing the surface condition of a PCBusing RGB colors, in which oxidation, contamination, and structuraldefects of the PCB are quantitatively measured, based on relative valuesof RGB signals, in unit pixels of an image obtained by picking up animage of the PCB.

[0016] In accordance with one aspect, the present invention provides asystem for analyzing a surface condition of a printed circuit board(PCB) using RGB colors, comprising: feeding means for feeding a targetPCB, to be measured, to an image pick-up position where pick-up means isdisposed; the pick-up means for picking up an image of a metal surfaceof the target PCB fed by the feeding means, and externally transmittingdata of the picked-up image; and signal analyzing means for settingrelative RGB values derived through a moisture absorption test carriedout for a comparative PCB at intervals of time, extracting pixel datafrom the picked-up image for the target PCB received from the pick-upmeans, performing a mapping operation for RGB signals of the extractedpixel data, thereby determining relative RGB values, and comparing thedetermined relative RGB values with the relative RGB values derivedthrough the moisture absorption test, thereby producing cumulativedistribution data of the relative RGB values for the target PCB.

[0017] In accordance with another aspect, the present invention providesa method for analyzing a surface condition of a printed circuit board(PCB) using RGB colors, comprising the steps of: setting relative RGBvalues for PCBs, and storing the set relative RGB values; picking up animage of a target PCB, to be measured, fed by a feeding unit; performingan RGB-mapping process for pixel data extracted from the picked-up imageof the target PCB; and producing accumulative distribution data ofrelative RGB values for the pixel data of the target PCB, therebyquantitatively determining an oxidation degree of the target PCB.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above objects, and other features and advantages of thepresent invention will become more apparent after reading the followingdetailed description when taken in conjunction with the drawings, inwhich:

[0019]FIG. 1 is a block diagram illustrating a system for analyzing thesurface condition of a PCB using RGB colors in accordance with thepresent invention;

[0020]FIG. 2 is a schematic view illustrating pixel data produced byRGB-mapping an image of the metal surface of a PCB by a certain mappingprogram in accordance with the present invention;

[0021]FIG. 3 is a graph depicting the correlation between the O₂ contentof the PCB metal surface and the relative values of RGB signals varyingby the lapse of time;

[0022]FIG. 4 is a histogram depicting cumulative distribution data offractions and relative values of RGB signals in pixel data associatedwith the metal surface of the PCB in accordance with the presentinvention;

[0023]FIG. 5 is a flow chart illustrating a method for analyzing thesurface condition of a PCB using RGB colors in accordance with thepresent invention;

[0024]FIG. 6 is a flow chart illustrating a routine for setting relativevalues associated with a metal surface of the PCB, and storing the setrelative values in a database in accordance with the present invention;

[0025]FIG. 7 is a flow chart illustrating a routine for picking up animage of the PCB metal surface by a pick-up unit in accordance with thepresent invention;

[0026]FIG. 8 is a flow chart illustrating a routine for RGB-mappingpixel data extracted from the image of the PCB metal surface inaccordance with the present invention; and

[0027]FIG. 9 is a flow chart illustrating a routine for quantitativelydetermining the oxidation degree of the PCB exhibited with the lapse oftime, based on cumulative distribution data of RGB signals in accordancewith the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Now, a system for and a method of analyzing the surface conditionof a PCB using RGB signals in accordance with the present invention willbe described in detail with reference to the annexed drawings.

[0029] First, the configuration and operation of the system foranalyzing the surface condition of a PCB using RGB signals in accordancewith the present invention will be described in detail with reference toFIG. 1.

[0030] Referring to FIG. 1, a feeding unit 100 is shown which carries aPCB, to be measured, thereon, and feeds the PCB to an image pick-upposition where a pick-up unit 200 to be described hereinafter isdisposed. The feeding unit 100 includes a conveyor belt connected to aproduction line for PCBs, and adapted to feed a PCB to the image pick-upposition, a sensor installed at a predetermined position on the conveyorbelt, and adapted to sense the operating state of the conveyor, acontrol signal input/output unit for receiving, from a signal analyzingunit 300, a control signal adapted to control the operation of thefeeding unit, and a control unit for controlling the whole of thefeeding unit.

[0031] Although the feeding unit has been described as using theconveyor belt, it is not limited thereto. It may be possible to feed aPCB to the image pick-up position, using a feeding unit having aconfiguration different from that of the above described feeding unit.

[0032] The pick-up unit 200 picks up an image of the metal surface ofthe PCB fed by the feeding unit 100, divides data of the picked-up imageinto pixels of a corresponding bitmap, and stores luminance data of thepicked-up image data corresponding to each pixel in an internal memoryincluded in the pick-up unit 200.

[0033] When a signal requesting inputting of the image datacorresponding to the picked-up image of the PCB metal surface isinputted from the signal analyzing unit 300 via a certain communicationinterface, for example, an RS232C communication interface, the pick-upunit 200 transmits the image data stored in the internal memory to thesignal analyzing unit 300.

[0034] For the pick-up unit 200 adapted to pick up the image of the PCBmetal surface, a digital camera, scanner or charge coupled device (CCD)may be used.

[0035] When the signal analyzing unit 300 receives the image data fromthe pick-up unit 200 via the communication interface, it maps the imagedata for a selected pixel, using RGB values in predetermined RGB ranges,and measures the degree of oxidation on the associated PCB metalsurface, based on the results of the mapping, thereby quantitativelydetermining whether or not the associated PCB has poor quality. As shownin FIG. 1, the signal analyzing unit 300 includes a datatransmitting/receiving unit 301, a light source setting unit 302, an RGBrange setting unit 303, a database 304, a signal converting unit 305,and a signal processing unit 306

[0036] The data transmitting/receiving unit 301 receives the picked-upimage data of the PCB metal surface inputted from the pick-up unit 200via the communication interface, and then sends the received image datato the signal processing unit 306.

[0037] The data transmitting/receiving unit 301 receives various controlsignals inputted through a data input unit such as a keyboard, to setsystem operating conditions, for example, a light source setting controlsignal adapted to set the color temperature and brightness of light, tobe irradiated onto the PCB upon picking up an image of the PCB, tocertain values, respectively, an RGB range setting control signaladapted to set RGB ranges to be used when RGB-mapping the picked-upimage data for a selected pixel, a control signal for controlling theoperation of the feeding unit 100, and an image pick-up control signalfor controlling the pick-up unit 200. The data transmitting/receivingunit 301 sends the received control signals to the signal processingunit 306.

[0038] The data transmitting/receiving unit 301 also receives cumulativedistribution data of fractions and relative values of R signalsassociated with the metal surface of the PCB, and transmits the receivedcumulative distribution data to a certain output device (not shown) suchas a computer monitor or printer via a certain communication interface.The cumulative distribution data is produced by the signal convertingunit 305.

[0039] The light source setting unit 302 performs a control operationfor light emitted from a light source to be used when picking up animage of the PCB metal surface. For example, the light source settingunit 302 controls the color temperature and brightness of the light.

[0040] Based on a control signal received from the signal processingunit 306, the RGB range setting unit 303 sets RGB ranges to be appliedto an RGB mapping process which will be performed for selected pixeldata of the PCB metal surface in accordance with a certain mappingprogram.

[0041] Each of the RGB ranges, that is, R, G, and B ranges, may be setto have level values of 0 to 255 respectively corresponding to differentintensity values of a corresponding one of R (red), G (green), and B(blue) signals associated with each pixel of the PCB surface image.

[0042] That is, each of the RGB signals, that is, R, G, and B signals,may be represented by 256 intensity levels respectively having levelvalues of 0 to 255. The number of different colors representable in thiscase is 256³ (R×G×B=16,777,216). That is, various colors can berepresented by appropriately combining various intensity values of R, G,and B signals. For example, black can be represented by an RGB intensitycombination of (0,0,0), bright red (255,0,0), bright green (0,255,0),yellow (255,255,0), cyan (0,255,255), magenta (255,0,255), and white(255,255,255).

[0043] The database 304 stores data of R signal fractions (%) andassociated relative values measured for the metal surface of the PCB.The R signal fractions are measured at intervals of, for example, 24hours after performing a moisture absorption test for the metal surfaceof the PCB under predetermined conditions of, for example, 85° C./60%RH/168 h. The relative value associated with each R signal fraction iscalculated by dividing the R signal fraction by an R signal fractionmeasured at normal temperature for the metal surface of a general PCBnot subjected to any moisture absorption test. The following Table 1shows data of R signal fractions and associated relative values measuredat intervals of 24 hours for the metal surface of the PCB afterperforming a moisture absorption test under the conditions of 85° C./60%RH/168 h. TABLE 1 Results of RGB Color Analysis of Metal Surface underThe Conditions of 85° C./60% RH/168 h Conditions Red Signal Fraction (%)Relative Value 85° C./60% RH/0 h 22.573 1.000 85° C./60% RH/24 h 27.0941.200 85° C./60% RH/48 h 27.879 1.235 85° C./60% RH/72 h 29.698 1.31685° C./60% RH/96 h 46.071 2.041 85° C./60% RH/120 h 67.312 2.982 85°C./60% RH/144 h 67.993 3.012 85° C./60% RH/168 h 67.994 2.012

[0044] The database 304 also stores data of R signal fractions measuredat intervals of time for the metal surface of the PCB after performing amoisture absorption test under severer conditions than those of Table 1,that is, the conditions of 85° C./85% RH/168 h, and associated relativevalues each measured for the metal surface of the PCB by dividing theassociated R signal fraction by an R signal fraction measured at normaltemperature for the metal surface of a general PCB not subjected to anymoisture absorption test. The data of R signal fractions and associatedrelative values are shown in the following Table 2. TABLE 2 Results ofRGB Color Analysis of Metal Surface under The Conditions of 85° C./85%RH/168 h Red Signal Relative O₂ Condition Fraction (%) Value Content (%)85° C./85% RH/0 h 22.573 1.000  4.021 85° C./85% RH/24 h 35.124 1.556 5.214 85° C./85% RH/168 h 73.074 3.237 16.721

[0045] The surface condition of the PCB varying with the lapse of timeand R signal fraction data representing the variation in PCB surfacecondition will now be described in detail with reference to Tables 1 and2.

[0046] Referring to Table 1, it can be seen that R signal fractions, andtherefore, oxidation degrees, measured at intervals of time for themetal surface of the PCB after performing a moisture absorption testunder the conditions of 85° C./60% RH/168 h are distributed in a rangefrom about 22% to about 67%. It can also be seen that relative valuesrespectively associated with the R signal fractions are distributed in arange from about 1.00 to about 3.01.

[0047] That is, where oxidation caused by adsorption of moisture isperformed for 168 hours, a great increase in R signal fraction isexhibited in a period of time after 72 hours, but before 120 hours. Sucha phenomenon is caused by a great increase in the thickness ordistribution of oxides formed on the metal surface of the PCB inaccordance with oxidation of the metal surface.

[0048] After 120 hours, a substantially constant R signal fraction isexhibited. This is because levels of R signals are substantially uniformin accordance with an increase in the scattering degree of reflectivevisible rays caused by the greatly increased thickness or distributionof oxides on the metal surface of the PCB.

[0049] Referring to Table 2, it can be seen that R signal fractions, andtherefore, oxidation degrees, measured at intervals of time for themetal surface of the PCB after performing a moisture absorption testunder severe conditions of 85° C./85% RH/168 h are distributed in arange from about 22% to about 73%. It can also be seen that relativevalues respectively associated with the R signal fractions aredistributed in a range from about 1.00 to about 3.2. These distributionsof R signal fractions and relative values are similar to those of Table1.

[0050]FIG. 3 shows the correlation between the O₂ content of the PCBmetal surface at a pixel and the relative values of RGB signals, inparticular, the relative value of the R signal, at the pixel. Referringto FIG. 3, it can be seen that the relative value of the R signal andthe O₂ content (%) varies sharply in a period of time after 72 hours,but before 120 hours.

[0051] The signal converting unit 305 converts a relative R signalvalue, received from the signal processing unit 306 for a selected pixelof the PCB metal surface image, into an electrical signal. In responseto a control signal from the signal processing unit 306, the signalconverting unit 305 sends cumulative distribution data associated withthe PCB metal surface to the data transmitting/receiving unit 301.

[0052] The signal processing unit 306 receives various control signalsinputted by the operator through a data input unit such as a keyboard,to set system operating conditions, for example, a light source settingcontrol signal adapted to set the color temperature and brightness oflight, to be irradiated onto the metal surface of a target PCB, to bemeasured, upon picking up an image of the PCB, to certain values,respectively, an RGB range setting control signal adapted to set RGBranges to be used upon RGB-mapping of the picked-up image data for aselected pixel, a control signal for controlling the operation of thefeeding unit 100, and an image pick-up control signal for controllingthe pick-up unit 200. Based on the received control signals, the signalprocessing unit 306 performs associated control operations,respectively.

[0053] The signal processing unit 306 also receives, from the datatransmitting/receiving unit 301, the image data of the PCB metal surfaceinputted from the pick-up unit 200 to the data transmitting/receivingunit 301 through the communication interface. The signal analyzing unit300 then runs a mapping program, thereby mapping the image data for aselected pixel, using RGB values in predetermined RGB ranges, as shownin FIG. 2.

[0054] Thereafter, the signal processing unit 306 detects RGB signals,in particular, an R signal, from the pixel data of the PCB metal surfaceimage mapped based on the RGB values in the predetermined RGB ranges,and then analyzes the detected R signal associated with the metalsurface of the target PCB by comparing the relative value of the Rsignal with respective relative values of R signals measured atintervals of time for the metal surface of a comparative PCB and storedin the database.

[0055] The signal processing unit 306 then sends the relative values ofR signals associated with the PCB metal surface to the signal convertingunit 305 via the communication interface. Based on the relative valuesof R signals, the signal converting unit 305 produces cumulativedistribution data of RGB signals in the PCB metal surface image.

[0056] Based on the cumulative distribution data representing relativevalues of RGB signals associated with the metal surface of the PCB, thedegree of oxidation generated on the PCB is quantitatively determined.

[0057] Now, a method for analyzing the surface condition of a PCB, basedon RGB colors, using the analyzing system having the above describedconfiguration, will be described in detail with reference to FIGS. 5 to9.

[0058] In accordance with the analyzing method, the signal analyzingunit 300 stores relative RGB values measured at intervals of time forthe metal surface of a comparative PCB treated under a predeterminedcondition, as shown in FIG. 5 (S100).

[0059] This routine will be described in more detail with reference toFIG. 6. A moisture absorption test is carried out for the metal surfaceof the comparative PCB under certain conditions, for example, conditionsof 85° C./60% RH/168 h corresponding to the Level II of JEDEC (JointElectron Device Engineering Council), or severer conditions of 85°C./85% RH/168 h, as shown in Table 1 or Table 2 (S101).

[0060] After execution of the moisture absorption test under the abovedescribed conditions, the signal analyzing unit 300 measures, atintervals of time, the R signal fraction for the metal surface of thecomparative PCB varying with the lapse of time (S102). The signalanalyzing unit 300 then divides each R signal fraction measured at stepS102 by a corresponding R signal fraction measured at normal temperaturefor the metal surface of a general PCB not subjected to any moistureabsorption test, thereby deriving a relative RGB value (S103).

[0061] The R signal fraction represents the degree of oxidationgenerated on the metal surface of the PCB. A higher R signal fractionrepresents an increased oxidation of the PCB metal surface.

[0062] Thereafter, the signal analyzing unit 300 stores the derivedrelative value in the database 304 so that its signal processing unit306 may use the stored relative value as comparative data when acorresponding R signal value for the metal surface of a target PCB, tobe measured, is subsequently inputted to the data transmitting/receivingunit 301 through a certain input unit such as a keyboard or scanner(S104).

[0063] After the signal analyzing unit 300 completely stores, in thedatabase 304, the relative values measured at intervals of time for themetal surface of the comparative PCB, the pick-up unit 20 picks up animage of the metal surface of a target PCB fed by the feeding unit 100for measurement thereof, under the control of the signal analyzing unit300, as shown in FIG. 5 (S200).

[0064] This routine will be described in detail with reference to FIG.7. When the target PCB reaches the image pick-up position where thepick-up unit 200, which may be a digital camera, scanner, or CCD camera,is disposed, in accordance with the feeding operation of the feedingunit 100 (S201), the signal processing unit 306 of the signal analyzingunit 100 determines whether or not the color temperature and brightnessof light to be used upon picking up an image of the PCB are set topredetermined values, respectively (S202).

[0065] Where it is determined at step S202 that the color temperatureand brightness of light to be used upon picking up an image of the PCBare set to predetermined values, respectively, the signal processingunit 306 of the signal analyzing unit 300 sends a control signal,adapted to control the operation of the pick-up unit 200 for picking upan image of the PCB, to the pick-up unit 200 via the datatransmitting/receiving unit 301 (S204).

[0066] In response to the image pick-up control signal received from thedata transmitting/receiving unit 301 of the signal analyzing unit 300,the pick-up unit 200 picks up an image of the metal surface of thetarget PCB (S205). The pick-up unit 200 then divides data of thepicked-up image into pixels of a corresponding bitmap, and producesrespective image data files of the pixels (S206).

[0067] After completion of the image pick-up operation for the metalsurface of the target PCB by the pick-up unit 200, the signal analyzingunit 300 runs the mapping program, thereby mapping the image datareceived from the pick-up unit 200 for a selected pixel, as shown inFIG. 5 (S300).

[0068] This routine will be described in detail with reference to FIG.8. When the signal analyzing unit 300 receives the image data of the PCBmetal surface via the communication interface (S301), its signalprocessing unit 306 runs the mapping program, selects an optional pixelfrom the bitmap image data, and extracts associated pixel data from thebitmap image data (S302).

[0069] Thereafter, the signal processing unit 306 determines whether ornot reliable RGB signals are detected from the extracted pixel data ofthe selected pixel (S303).

[0070] When it is determined at step S303 that reliable RGB signalscannot be detected from the extracted pixel data of the selected pixel,the signal processing unit 306 repeats selection of another pixel andextraction of associated pixel data until reliable RGB signals aredetected (S304).

[0071] On the other hand, when it is determined at step S303 thatreliable RGB signals are detected from the extracted pixel data of theselected pixel, the signal processing unit 306 determines whether or notoptimum RGB ranges for RGB-mapping of the image data have been set(S305).

[0072] Where it is determined at step S305 that the optimum RGB rangesfor RGB-mapping of the image data have not been set, the signalprocessing unit 306 sends a control signal for setting of the optimumRGB ranges to the RGB range setting unit 303, so that the optimum RGBranges are set in accordance with an operation of the RGB range settingunit 303 (S306).

[0073] On the other hand, where it is determined at step S305 that theoptimum RGB ranges for RGB-mapping of the image data have been set, thesignal processing unit 306 performs an RGB mapping operation for aselected pixel of the image data by running the mapping program, asshown in FIG. 2 (S307).

[0074] After RGB-mapping the image data of the PCB metal surface for theselected pixel, the signal analyzing unit 300 produces cumulativedistribution data of relative RGB values for the selected pixel of thePCB, and quantitatively determines the degree of oxidation of the PCB,based on the cumulative distribution data (S400).

[0075] This routine will be described in detail with reference to FIG.9. The signal processing unit 306 of the signal analyzing unit 300detects RGB signals, in particular, an R signal, from a selected pixelof the PCB metal surface image by running the mapping program (S401),and then measures the R signal fraction (%) and relative value of thedetected R signal (S402).

[0076] Thereafter, the signal processing unit 306 searches data storedin the database 304 for data associated with the same R signal fractionand relative value as the measured R signal fraction and relative value(S403).

[0077] The signal processing unit 306 then sends the searched data tothe signal converting unit 305 in order to convert the searched datainto an electrical signal (S404).

[0078] Subsequently, the signal processing unit 306 receives, from thesignal converting unit 305, the electrical signal representing the Rsignal fraction and relative value (S405), and then controls the signalconverting unit 305 to produce cumulative distribution data, as shown inFIG. 4 (S406).

[0079] Based on the cumulative distribution data of RGB signals producedin association with the metal surface of the PCB in the above describedroutine, the signal processing unit 306 quantitatively determines thedegree of oxidation generated on the metal surface of the target PCB,thereby determining whether or not the target PCB has poor quality(S407).

[0080] As apparent from the above description, the present inventionprovides a system for and a method of analyzing the surface condition ofa PCB using RGB colors, which can analyze relative values of RGB colorsin an image picked up from the metal surface of a PCB, thereby rapidlyand easily analyzing the surface condition of the PCB such as oxidation,contamination, or structural defects of the PCB in a quantitativemanner.

[0081] In accordance with the present invention, the measure fordetermining poor quality of PCBs is set in a relative or quantitativemanner, based on cumulative distribution data of relative RGB values inthe picked-up PCB image. Accordingly, it is possible to considerablyreduce the rate of PCBs having poor quality, as compared to theconventional method in which the determination of PCBs having poorquality is achieved with the operator's naked eye.

[0082] Although the preferred embodiments of the invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

What is claimed is:
 1. A system for analyzing a surface condition of aprinted circuit board (PCB) using RGB colors, comprising: feeding meansfor feeding a target PCB, to be measured, to an image pick-up positionwhere pick-up means is disposed; the pick-up means for picking up animage of a metal surface of the target PCB fed by the feeding means, andexternally transmitting data of the picked-up image; and signalanalyzing means for setting relative RGB values derived through amoisture absorption test carried out for a comparative PCB at intervalsof time, extracting pixel data from the picked-up image of the targetPCB received from the pick-up means, performing a mapping operation forRGB signals of the extracted pixel data, thereby determining relativeRGB values, and comparing the determined relative RGB values with therelative RGB values derived through the moisture absorption test,thereby producing cumulative distribution data of the relative RGBvalues for the target PCB.
 2. The system according to claim 1, whereinthe pick-up means comprises a digital camera, a scanner, or a chargecoupled device.
 3. The system according to claim 1, wherein the signalanalyzing means comprises: a data transmitting/receiving unit forreceiving the picked-up image data from the pick-up means, andoutputting the cumulative distribution data of the relative RGB valuesfor the target PCB produced in accordance with the RGB-mappingoperation; a light source setting unit for setting a color temperatureand brightness of light to be used upon picking up the image of thetarget PCB; an RGB range setting unit for setting RGB ranges to beapplied to a mapping operation to be carried out for the picked-up imageof the target PCB in the unit of pixels in accordance with a mappingprogram; a database for storing the set relative RGB values representingthe oxidation degree of the comparative PCB subjected to the moistureabsorption test; a signal converting unit for converting the relativeRGB values derived for the target PCB into an electrical signal; and asignal processing unit for transmitting a light source setting controlsignal, an RGB range setting control signal, a control signal adapted tocontrol an operation of the feeding means, and an image pick-up controlsignal to the light source setting unit, the RGB range setting unit, thefeeding unit, and the pick-up means, respectively, receiving thepicked-up image data inputted through the data transmitting/receivingunit, extracting pixel data from the received picked-up image data for aselected pixel, performing an RGB mapping operation for the extractedpixel data, and determining relative RGB values from the RGB-mappedpixel data, thereby producing cumulative distribution data.
 4. Thesystem according to any one of claims 1 to 3, wherein the RGB signalsonly have R signal components.
 5. The system according to claim 1,wherein the feeding means comprises: a conveyor belt connected to aproduction line for PCBs, and adapted to feed a PCB from the productionline to the image pick-up position; a sensor installed at apredetermined position on the conveyor belt, and adapted to sense anoperating state of the conveyor; a control signal input/output unit forreceiving, from the sensor, a sensing signal representing the sensedoperating state of the conveyer, and transmitting the sensing signal tothe signal analyzing means, the control signal input/output unit alsoreceiving, from the signal analyzing means, a control signal adapted tocontrol an operation of the feeding means; and a control unit forcontrolling the operation of the feeding means, based on the controlsignal.
 6. A method for analyzing a surface condition of a printedcircuit board (PCB) using RGB colors, comprising the steps of: (A)setting relative RGB values for PCBs, and storing the set relative RGBvalues; (B) picking up an image of a target PCB, to be measured, fed bya feeding unit; (C) performing an RGB-mapping process for pixel dataextracted from the picked-up image of the target PCB; and (D) producingaccumulative distribution data of relative RGB values for the pixel dataof the target PCB, thereby quantitatively determining an oxidationdegree of the target PCB.
 7. The method according to claim 6, whereinthe step (A) comprises the steps of: performing a moisture absorptiontest for a metal surface of a PCB under a predetermined condition;measuring values of RGB signals detected from the PCB with the lapse oftime after the moisture absorption test; dividing each of the measuredRGB signal values by a corresponding RGB signal value obtained for a PCBnot subjected to the moisture absorption test, thereby measuringrelative RGB values; and storing the relative RGB values in the databaseto use the stored relative RGB values as comparative data for measuringthe oxidation degree of the target PCB.
 8. The method according to claim6, wherein the step (B) comprises the steps of: feeding the target PCBto an image pick-up position where a pick-up unit is disposed, inaccordance with a feeding operation of the feeding unit; determiningwhether or not a color temperature and brightness of light to beirradiated onto the target PCB upon picking up an image of the targetPCB are set to predetermined values, respectively; if the colortemperature and brightness of the light are not set to the predeterminedvalues, respectively, sending a control signal, adapted to set the colortemperature and brightness of the light to the predetermined values,from a signal analyzing unit to a light source setting unit; sending animage pick-up control signal, adapted to pick up an image of the PCB,from the signal analyzing unit to the pick-up unit; and picking up animage of a metal surface of the PCB in accordance with the image pick-upcontrol signal, dividing the picked-up image into pixels of acorresponding bitmap, and producing an image data file of the bitmap. 9.The method according to claim 6, wherein the step (C) comprises thesteps of: receiving the picked-up image data of the PCB from the pick-upunit via a communication interface by the signal analyzing unit; runninga mapping program by the signal analyzing unit, thereby extracting pixeldata from the picked-up image data of the PCB for a selected pixel;determining whether or not reliable RGB signals are detected from thepixel data extracted by the signal analyzing unit; if reliable RGBsignals are not detected from the extracted pixel data, repeating thepixel data extraction step and the determination step until reliable RGBsignals are detected; determining whether or not optimum RGB ranges formapping of the pixel data have been set by the signal analyzing unit; ifthe optimum RGB ranges for mapping of the pixel data have not been set,sending a control signal, adapted to set the optimum RGB ranges for themapping of the pixel data, from the signal analyzing unit to the RGBrange setting unit, thereby setting the optimum RGB ranges; and runningthe mapping program by the signal analyzing unit, thereby RGB-mappingthe pixel data of the PCB.
 10. The method according to claim 6, whereinthe step (D) comprises the steps of: running a mapping program by thesignal analyzing unit, thereby extracting RGB signals from the pixeldata of the target PCB; running the mapping program by the signalanalyzing unit, thereby determining a relative RGB value from theextracted RGB signals; comparing the determined relative RGB value witha corresponding relative RGB value searched for from a database storedwith relative RGB values, and converting the determined relative RGBvalue into an electrical signal; and running the mapping program by thesignal analyzing unit, thereby producing cumulative distribution data ofrelative RGB values of pixel data for the target PCB, and quantitativelydetermining an oxidation degree of the target PCB exhibited with thelapse of time, based on the cumulative distribution data.